Please help with a, b, c, and d. Currently practicing for AP exam but stuck have not been able to figure this one out.

Particle O moves along the x-axis so that its velocity at any time f is given by vo(!) = 1 - 3 cos and its (c) A second particle, R, moves along the x-axis so that its position at any time / is given by a differentiable acceleration at any time f is given by an(t) = sin function XR(1), where xR(1) = 4 and XR(3) = 8. Explain why there must be a time /, for ]